86
ALFRED J . COULOMBRE
The intermediate cell layers arise relatively late in most species. In
the mouse these cells remain separated from one another by large, extensive, intercellular spaces which disappear progressively as the number of cell membrane interdigitations increases (Sheldon, 1956). The cells
contain scattered glycogen granules and moderate amounts of disulfide
and sulfhydryl groups (Calmettes et ah, 1956). In man the anterior epithelium completes the transition to the two layered condition following
the 3rd month when the lids have fused. After 5^ or 6 months of
gestation, when the lids reopen, the intermediate layers are added
(Vasilyeva, 1957).
The basal cells are cuboidal or columnar. They interdigitate with one
another less frequently than the intermediate cells. The nucleus is indented and its membrane is studded with pores (Sheldon, 1956).
The maturation of the anterior epithelium is reflected chemically as
well as morphologically. Kuhlman and Resnik (1958) used the postpartum rat to show an increase in the specific activity of lactic dehydrogenase, glucose-6 phosphate dehydrogenase, and isocitric dehydrogenase
in the anterior epithelium between birth and 20 days post partum. The
oxidative pathway remained more active throughout development than
the Emden-Meyerhof pathway.
The basal cells of the anterior epithelium of the cornea are underlain
by a basement membrane (Calmettes et ah, 1956; Offret and Haye,
1959). Offret and Haye note that this membrane is present from very
early stages in development. Indeed, it appears to arise directly from
the basement membrane which underlies the primitive ectoderm prior
to the time when the cornea is induced (O'Rahilly and Meyer, 1960). I t
adheres closely to the epithelium and regenerates with the epithelium
following wounding of the cornea (Busacca, 1949). I t is PAS + , orthochromatic with toluidine blue, contains lipid and reticulin, but is devoid
of glycogen (Calmettes et ah, 1956). In the newborn mouse this
membrane is about 600 Â thick and is cross-banded (Sheldon, 1956).
The anterior epitheUum serves many functions. I t has, for example,
notable regenerative power. When the adult anterior epithelium is
wounded, adjacent epithelial cells migrate into the wound area (Friedenwald and Buschke, 1944). This migration constitutes the initial phase of
epithelial wound healing and is inhibited by quinones, naphthaquinones,
iodacetate, mercurials, and arsenicals (Buschke, 1947). Migratory
activity is inversely related to temperature in the frog, and has a Q 10 of
3 (Buschke, 1948). The Q 10 for this process in the rat is 5 (Friedenwald,
1944). In the next phase of wound healing the cells of the epithelium,
both in the wound area and at some distance from it, show an increase
in mitotic rate following wounding (Buschke, 1949; Friedenwald,
1944, 1950; Friedenwald and Buschke, 1944; Friedenwald et ah, 1945).
ALFRED J . COULOMBRE
The intermediate cell layers arise relatively late in most species. In
the mouse these cells remain separated from one another by large, extensive, intercellular spaces which disappear progressively as the number of cell membrane interdigitations increases (Sheldon, 1956). The cells
contain scattered glycogen granules and moderate amounts of disulfide
and sulfhydryl groups (Calmettes et ah, 1956). In man the anterior epithelium completes the transition to the two layered condition following
the 3rd month when the lids have fused. After 5^ or 6 months of
gestation, when the lids reopen, the intermediate layers are added
(Vasilyeva, 1957).
The basal cells are cuboidal or columnar. They interdigitate with one
another less frequently than the intermediate cells. The nucleus is indented and its membrane is studded with pores (Sheldon, 1956).
The maturation of the anterior epithelium is reflected chemically as
well as morphologically. Kuhlman and Resnik (1958) used the postpartum rat to show an increase in the specific activity of lactic dehydrogenase, glucose-6 phosphate dehydrogenase, and isocitric dehydrogenase
in the anterior epithelium between birth and 20 days post partum. The
oxidative pathway remained more active throughout development than
the Emden-Meyerhof pathway.
The basal cells of the anterior epithelium of the cornea are underlain
by a basement membrane (Calmettes et ah, 1956; Offret and Haye,
1959). Offret and Haye note that this membrane is present from very
early stages in development. Indeed, it appears to arise directly from
the basement membrane which underlies the primitive ectoderm prior
to the time when the cornea is induced (O'Rahilly and Meyer, 1960). I t
adheres closely to the epithelium and regenerates with the epithelium
following wounding of the cornea (Busacca, 1949). I t is PAS + , orthochromatic with toluidine blue, contains lipid and reticulin, but is devoid
of glycogen (Calmettes et ah, 1956). In the newborn mouse this
membrane is about 600 Â thick and is cross-banded (Sheldon, 1956).
The anterior epitheUum serves many functions. I t has, for example,
notable regenerative power. When the adult anterior epithelium is
wounded, adjacent epithelial cells migrate into the wound area (Friedenwald and Buschke, 1944). This migration constitutes the initial phase of
epithelial wound healing and is inhibited by quinones, naphthaquinones,
iodacetate, mercurials, and arsenicals (Buschke, 1947). Migratory
activity is inversely related to temperature in the frog, and has a Q 10 of
3 (Buschke, 1948). The Q 10 for this process in the rat is 5 (Friedenwald,
1944). In the next phase of wound healing the cells of the epithelium,
both in the wound area and at some distance from it, show an increase
in mitotic rate following wounding (Buschke, 1949; Friedenwald,
1944, 1950; Friedenwald and Buschke, 1944; Friedenwald et ah, 1945).